The answer is a possible ACL or route-map misconfiguration causing the third translation to use basic NAT instead of PAT. The output shows two PAT translations for 10.0.0.10, both using the same inside global address 192.0.2.10 with protocol and port numbers, while the third entry for 10.0.0.11 lacks a protocol column, indicating a one-to-one dynamic NAT translation that does not leverage port address translation. This inconsistency with the configured `overload` keyword on the pool suggests that traffic from 10.0.0.11 is not being matched by ACL1 or is being caught by a route-map that disables PAT for that specific flow. On the CCNP ENARSI 300-410 exam, this scenario tests your ability to interpret `show ip nat translations` mixed PAT and basic NAT entries, a common trap where candidates overlook the missing protocol field as a sign of misconfiguration. Remember the memory tip: “No protocol, no overload—check your ACL or route-map for the missing fold.”
300-410 NAT and PAT Practice Question
This 300-410 practice question tests your understanding of nat and pat. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A network engineer runs the following command on Router R1:
R1# show ip nat translations
Pro Inside global Inside local Outside local Outside global
udp 192.0.2.10:1234 10.0.0.10:1234 203.0.113.5:53 203.0.113.5:53
tcp 192.0.2.10:5678 10.0.0.10:5678 198.51.100.20:80 198.51.100.20:80
--- 192.0.2.11 10.0.0.11 --- ---
The third translation is not using PAT, indicating a possible ACL or route-map misconfiguration.
The overload configuration should create PAT entries with protocol/port. The third entry without protocol suggests the traffic from 10.0.0.11 is not being matched by the same ACL or is using a different pool.
B
The pool is exhausted because 192.0.2.10 is used twice.
Why wrong: PAT allows multiple inside hosts to share the same global address; this is normal. Exhaustion would occur if all pool addresses were used without overload.
C
The outside interface is misconfigured as inside.
Why wrong: The statistics show correct interface assignment.
D
The NAT translations are all static.
Why wrong: The statistics clearly show 0 static translations.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The third translation is not using PAT, indicating a possible ACL or route-map misconfiguration.
The output shows two PAT translations (UDP and TCP) for 10.0.0.10 using the same inside global address 192.0.2.10, plus a dynamic NAT translation for 10.0.0.11 without protocol/port. The problem is that the third translation (10.0.0.11) is not using PAT (no port), which could indicate a misconfiguration or that ACL1 does not match traffic from 10.0.0.11 properly, or that the pool is misapplied. However, the key clue is that the third entry lacks a protocol, meaning it is a basic NAT translation, not PAT, which is inconsistent with the overload configuration. This could be due to a route-map or ACL issue.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
The third translation is not using PAT, indicating a possible ACL or route-map misconfiguration.
Why this is correct
The overload configuration should create PAT entries with protocol/port. The third entry without protocol suggests the traffic from 10.0.0.11 is not being matched by the same ACL or is using a different pool.
The pool is exhausted because 192.0.2.10 is used twice.
Why it's wrong here
PAT allows multiple inside hosts to share the same global address; this is normal. Exhaustion would occur if all pool addresses were used without overload.
✗
The outside interface is misconfigured as inside.
Why it's wrong here
The statistics show correct interface assignment.
✗
The NAT translations are all static.
Why it's wrong here
The statistics clearly show 0 static translations.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Trap categories for this question
Command / output trap
The statistics show correct interface assignment.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 300-410 subnetting questions on CIDR, address ranges, and subnet selection.
NAT and PAT — This question tests NAT and PAT — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The third translation is not using PAT, indicating a possible ACL or route-map misconfiguration. — The output shows two PAT translations (UDP and TCP) for 10.0.0.10 using the same inside global address 192.0.2.10, plus a dynamic NAT translation for 10.0.0.11 without protocol/port. The problem is that the third translation (10.0.0.11) is not using PAT (no port), which could indicate a misconfiguration or that ACL1 does not match traffic from 10.0.0.11 properly, or that the pool is misapplied. However, the key clue is that the third entry lacks a protocol, meaning it is a basic NAT translation, not PAT, which is inconsistent with the overload configuration. This could be due to a route-map or ACL issue.
What should I do if I get this 300-410 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 300-410 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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